PostgreSQL查看数据库，索引，表空间大小_pg 表空间大小和所有表大小加起来不一致

作者：weixin_40725706 | 2024-03-19 01:42:07

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pg 表空间大小和所有表大小加起来不一致

实例讲解

3.1 查看存储一个指定的数值需要的字节数

david=# select pg_column_size(1);
pg_column_size
----------------
4
(1 row)

david=# select pg_column_size(10000);
pg_column_size
----------------
4
(1 row)

david=# select pg_column_size('david');
pg_column_size
----------------
6
(1 row)

david=# select pg_column_size('hello,world');
pg_column_size
----------------
12
(1 row)

david=# select pg_column_size('2013-04-18 15:17:21.622885+08');
pg_column_size
----------------
30
(1 row)

david=# select pg_column_size('中国');
pg_column_size
----------------
7
(1 row)

david=# 3.2 查看数据库大小

查看原始数据

david=# select count(1) from test;
count
---------
1835008
(1 row)

david=# 查看david 数据库大小

david=# select pg_database_size('david');
pg_database_size
------------------
190534776
(1 row)

david=# 查看所有数据库大小

david=# 这样查出来的结果，看上去太长了，不太容易读数。

3.3 以人性化的方式显示大小

david=# select pg_size_pretty(pg_database_size('david'));
pg_size_pretty
----------------
182 MB
(1 row)

david=# 3.4 查看单索引大小

david=# select pg_relation_size('idx_test');
pg_relation_size
------------------
41238528
(1 row)

david=# select pg_size_pretty(pg_relation_size('idx_test'));
pg_size_pretty
----------------
39 MB
(1 row)

david=#
david=# select pg_size_pretty(pg_relation_size('idx_join_date_test'));
pg_size_pretty
----------------
39 MB
(1 row)

david=# 3.5 查看指定表中所有索引大小

david=# select pg_indexes_size('test');
pg_indexes_size
-----------------
82477056
(1 row)

david=# select pg_size_pretty(pg_indexes_size('test'));
pg_size_pretty
----------------
79 MB
(1 row)

david=# idx_test 和idx_join_date_test 两个索引大小加起来差不多等于上面pg_indexes_size() 查询出来的索引大小。

3.6 查看指定schema 里所有的索引大小，按从大到小的顺序排列。

david=# select * from pg_namespace;
      nspname       | nspowner |               nspacl
--------------------+----------+-------------------------------------
pg_toast           |       10 |
pg_temp_1          |       10 |
pg_toast_temp_1    |       10 |
pg_catalog         |       10 | {postgres=UC/postgres,=U/postgres}
information_schema |       10 | {postgres=UC/postgres,=U/postgres}
public             |       10 | {postgres=UC/postgres,=UC/postgres}
(6 rows)

david=# 3.7 查看指定表大小

david=# select pg_relation_size('test');
pg_relation_size
------------------
95748096
(1 row)

david=# select pg_size_pretty(pg_relation_size('test'));
pg_size_pretty
----------------
91 MB
(1 row)

david=# 使用pg_table_size() 函数查看

david=# select pg_table_size('test');
pg_table_size
---------------
95789056
(1 row)

david=# select pg_size_pretty(pg_table_size('test'));
pg_size_pretty
----------------
91 MB
(1 row)

david=# 3.8 查看指定表的总大小

david=# select pg_total_relation_size('test');
pg_total_relation_size
------------------------
178266112
(1 row)

david=# select pg_size_pretty(pg_total_relation_size('test'));
pg_size_pretty
----------------
170 MB
(1 row)

david=# 3.9 查看指定schema 里所有的表大小，按从大到小的顺序排列。

david=# 3.10 查看表空间大小

david=# select spcname from pg_tablespace;
spcname
------------
pg_default
pg_global
(2 rows)

david=# select pg_tablespace_size('pg_default');
pg_tablespace_size
--------------------
28381579760
(1 row)

david=# select pg_size_pretty(pg_tablespace_size('pg_default'));
pg_size_pretty
----------------
26 GB
(1 row)

david=# 另一种查看方法：

david=# select pg_tablespace_size('pg_default')/1024/1024 as "SIZE M";
SIZE M
--------
27066
(1 row)

david=# select pg_tablespace_size('pg_default')/1024/1024/1024 as "SIZE G";
SIZE G
--------
26
(1 row)

david=#

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